Cooling devices for supercharged internal combustion engines



April 22, 1969 J. GRATZMULLER 3,

I COOLING DEVICES FOR SUPERCHARGED INTERNAL COMBUSTION ENGINES Filed Feb. 27. 1967 s Z IJ r J 28 5 Mu /V7018 JEAN Lou/S GRATlMl/LgA-A B QM.

WOZA/EYS United States Patent Int. Cl. E02b 29/04 US. Cl. 12341.31 4 Claims ABSTRACT OF THE DISCLOSURE A cooling system for a supercharged internal combustion engine having a liquid cooled jacket and supercharger air inlet means. The supercharger air inlet means is provided with a pair of serially arranged heat-exchanger means to lower the temperature of the supercharger air. The first of these heat-exchanger means receives cooling liquid from a liquid cooling circuit including the jacket of the internal combustion engine. The other of these heatexchangers is located in the air inlet means between the engine and the first heat-exchanger and forms the part of a separate liquid cooling circuit provided with a circulation pump and air-cooled radiator.

The present invention is concerned with improvements relating to cooling devices for supercharged internal combustion engines, the special object of these improvements being the better utilisation of radiators, and, in consequence, a reduction in the number of dimensions of these radiators and/or improved cooling.

The invention applies to Diesel motors which are supercharged and have only one cooling-circuit, and likewise to motors having several separate cooling-circuits.

It is known that high-power supercharged Diesel engines, for example these powering locomotives, have in general at least two distinct cooling-circuits:

1) A principal circuit, or high-temperature circuit, which effects the cooling of the motor proper and which comprises at least the engines water-jackets, a circulation pump and so-called high-temperature radiators,

(2) An auxiliary, or low-temperature circuit, which cools the supercharging air for the engine, the lubricating oil, and if necessary the oil of a hydraulic transmission, etc. Such an auxiliary circuit comprises at least one water/air supercharging heat-exchanger, a circulation pump, and in general, a water/oil heat-exchanger, except when the oil is cooled by a special auxiliary circuit.

In order to show the diiference between the high and low-temperature circuits, it can be indicated that the former must keep the engine water at temperatures of the order of 85 to 100 degrees C. (depending on whether the cooling system functions at atmospheric pressure or else is provided with pressurising means such as those described in French Pat. No. 1,252,170 and its additions Nos. 77,300, 78,838, 83,678, and in the French Pats. Nos. 1,338,447 and 1,339,626), while the latter circuit must keep the cooling-water of the supercharging air and/ or/ of the oil at temperatures in the region of 50 degrees C.

Given that the surrounding atmospheric air for cooling the radiators can reach and surpass 30 degrees C., it can be seen that the efficiency of the low-temperature radiators, which must function with a temperature-difference of about 20 degrees C. between the entry and the exit of the air, is much less than that of the high-temperature radiators, which, as is usual to save space, even if they receive at the entry the air issuing from the lowtemperature radiators, have a temperature difference of from 35 to 60 degrees C. If it is noted that the low-tem- 3,439,657 Patented Apr. 22, 1969 perature circuit, in order to cool the supercharging air and the lubricating oil, must evacuate about 1.3 times more calories when the engine is at full power, than the hightemperature (H.T.) circuit, it can be seen that cooling problems are above all caused by the low temperature (B.T.) circuit, which, in practice, forms one of the limits to the increase of supercharging values, and, as a result, to the increase in power. Thus it happens, in the case of high-power Diesel locomotive engines, that one must provide about 3 times as many B.T. radiators as H.T., the more so because, as a result of the necessity of saving space, the radiators must be arranged in curtain formation, ie in pairs of radiators placed one behind the other, resulting in the fact that a large proportion of these pairs is made up of two B.T. radiators, and that the efficiency of these pairs is poor.

The invention aims to provide a cooling process, and cooling means which will remedy the difficulties arising in the B.T. circuit. According to the invention, the supercharging air is cooled in two stages, respectively by means of the B.T. and H.T. circuits, as described in French Pat. No. 1,363,148, in the name of the same inventor, but a new arrangement of the H.T. circuit is used, which, going beyond the previous results, achieves advantageous results from the point of view of economy of construction and functioning behaviour of the cooling system.

The process according to the invention, in order to cool a supercharged engine comprising one H.T. and one -B.T. cooling circuit, consists in the diversion, in parallel on H.T. radiators, of part of the water issuing from the H.T. circuit, and in the evacuation by means of this water of part of the calories contained in the supercharging air which is to be cooled, thanks to which the quantity of calories to be evacuated by the B.T. circuit can be reduced to a determined extend, and the number or the surface of the B.T. radiators can be reduced.

Naturally, this reduction in the number of B.T. radiators is accompanied by an increase in the number of H.T. radiators, but, as was seen above, the cooling limitations in usual systems arose in the B.T. circuit. Moreover, by means of suitable choice of the abo-vementioned proportion, the number of H.T. and B.T. radiators can be balanced, so that each pair is made up of one H.T. and one B.T. radiator, improving the overall efliciency and considerably reducing, e.g. by about 30%, the total number of radiators.

A cooling arrangement according to the invention, for a supercharged internal combustion engine, comprises; one main cooling circuit or H.T. circuit for the cooling of the engine proper; at least one auxiliary cooling circuit or B.T. circuit for partially cooling the supercharging air; as well as an additional circuit, which is diverted from the main circuit, in order partially to cool the supercharging air. The H.T. circuit comprises at least the engines waterjacket, a pump and so-called H.T. radiators; the B.T. circuit comprises at least one primary water/ air supercharging heat-exchanger, one pump and so-called B.T. radiators; the diverted additional circuit is connected to the M.T. circuit in parallel on the H.T. radiators and comprises at least one secondary supercharging water/air heat-exchanger inserted into the said diverted circuit, the said secondary exchanger making up a first stage of supercharging air cooling, whose second stage is constituted by the primary exchanger.

In present supercharged engines, there is provided in the main circuit a circulation pump which has an output which is more than is necessary for efficient functioning of the radiators, the abundant output of this pump being intended to cause very rapid water-circulation in the jackets and cylinder-heads of the engine so as to avoid hot points.

.In an arrangement according to the invention, the abovementioned diverted circuit being connected in parallel to the H.T. radiators, the total output D of the circulation pump passes into the engine, as is desirable in accordance with the preceding. However, only a part d of this output passes into the H.T. radiators, which reduces the stresses to which these radiators are exposed as a result of the circulation, and allows a reduction in the cross-section of the channels, while the rest of the output D-d passes into the secondary supercharging water/air heat-exchanger.

In an arrangement according to the invention, it can be of advantage, in order to obtain the lowest possible temperature of air admitted to the engine, to provide a second independent auxiliary circuit, comprising at least one pump, one water/air heat-exchanger and B.T. radiators, this-second auxiliary circuit cooling only the lubricating oil, while the first auxiliary circuit effects only the second stage of cooling of the supercharging air whose first cooling stage is effected by the diverted circuit abovementioned.

The invention is used to particular advantage in Diesel locomotive engines; this application will be mentioned in more detail in the following whether these engines be of classic type or of the type which is greatly supercharged, with a low compression ratio, e.g. of the type described in the patent application in France No. 48,222 filed Feb. 3, 1966 for Improvements in Supercharged Diesel Engines in the name of the same inventor.

In these engines which are greatly supercharged but which have a low compression ratio, means must be provided allowing satisfactory functioning at low power (or on cold starting) as at full power. Thus there can be provided a heat-exchanger system with the task of keeping the supercharging air at an essentially constant temperature, as described in the abovementioned patent, or a variable compression ratio system can be provided to allow for the engines working conditions.

Engines of this type can with advantage comprise only a single cooling-circuit (the H.T. circuit equipped according to the invention, with a diverted circuit connected in parallel to the radiators). According to this embodiment the cooling-water circuit comprises: a main branch comprising at least one pump and the engines water-jackets, arranged in series; a primary diverted branch from the said main branch, comprising at least one water/surrounding air raidiator; and a secondary diverted branch from the said main branch comprising at least one water/super charging air heat-exchanger.

The present invention is a cooling process for internal combustion engines consisting in passing the entire output of the engines cooling-circuit water through the engines water-jackets, then in dividing this entire output into a primary part which, cooling, passes through the radiators and then returns to the engine, and into a secondary part which passes in exchange of heat with the supercharging air for the engine, then returning to the engine.

The present invention is also a cooling device for a supercharged internal combustion engine in which the water-cooling circuit comprises: a main branch comprising at least one pump and the engines water-jackets, arranged in series; a primary branch diverted from the said main branch, and comprising at least on water/surrounding air radiator; and a secondary branch diverted from the said main branch comprising at least one water/air heat-exchanger, the air being the engines supercharging arr.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 diagrammatically illustrates an embodiment of a cooling system according to the invention;

FIGS. 2 and 3 are respectively vertical and horizontal sections showing an arrangement of the radiators of this cooling system on board a locomotive;

FIG. 4 is a diagram of another embodiment of the coling system, with independent cooling circuit for the engines lubricating oil; and

FIG. 5 is a horizontal section of the arrangement of the radiators as in FIG. 4.

The cooling system of the supercharged Diesel engine 2 shown in FIG. 1 comprises an H.T. circuit 4, a B.T. circuit 6, and a circuit 8, diverted from the H.T. circuit.

The H.T. circuit 4 comprises at least one radiator (or a group of radiators) 10, a pump 12, the engines waterjackets and the connecting pipes 14-16-18.

The B.T. circuit comprises at least one radiator (or group of radiators) 20, a pump 22, a water/oil heat-exchanger 24 cooling the engines lubricating oil (the pipes leading the oil to the exchanger are not shown) and a water/supercharging air heat-exchanger 26 which constitutes the B.T. stage of an exchanger 28 cooling the air blown by the supercharging turbo-compressor (not shown) of the engine. The circuit is completed by connecting pipes 30-32-34-36.

The H.T. diverted circuit 8 comprises simply a water/ supercharging air heat-exchanger 38 which constitutes the H.T. stage of the exchanger 28, the said exchanger being connected as a diversion from the main circuit, in parallel on the radiator 10, by means of two pipes 40-42.

The two radiators or groups of radiators 20-10 are arranged in pairs i.e. one behind the other, and are successively exposed to the flow of air caused by one or more ventilators 44.

Shown on FIGS. 2 and 3 is the curtain formation of the radiators aboard a locomotive with diesel engine 46, the radiators being grouped in pairs in two curtains on each side of the locomotive.

In order that each pair of radiators 20-10 be put to the best possible use, each pair must be made up of one B.T. radiator and one H.T. radiator. The invention allows this to be achieved, whereas in conventional cooling systems, the importance of the B.T. circuit led to its having many more B.T. radiators, especially since at full power this B.T. circuit had on its own to cool all the supercharging air, the temperature of this air being of the order of 200 degrees C. on leaving the compressor for a compression ratio of about 3. There therefore resulted the fact that certain pairs were made up of two B.T. radiators, of which the second one worked badly.

The connection of the new circuit 8, diverted from the radiators 10, has numerous advantages; in fact all the output of the pump 12 goes through the engines waterjackets, which helps to avoid hot points, whereas the part 14-10-16 is only passed through by a fraction of this output, e.g. about half. The result is that the cross-section of the pipes :14 and 16 (which are long) can be reduced, which is more economical and makes assembly easier, while at the same time the H.T. radiators 10 are no longer exposed to a violent and abundant output. Naturally, the other fraction of the output of the pump 12 (eg, the other half) passes through the supplementary pipes 40- 42 of the diverted circuit, but these pipes are extremely short (between the engine and the supercharging air inlet) and are therefore inexpensive.

On the other hand, the two-stage exchanger 28 is not much more important than the single exchanger which exists in conventional cooling systems.

Part of the calories of the supercharging air being evacuated by the new diverted circuit 8, the output of pump 22 of the B.T. circuit '6 no longer need be so large as in conventional cooling systems, so that a new economy is effected, on the pump and in the cross-section of the pipes 30-32-34-36 which are long.

The distribution of the output of the pump 12 between the two circuits 14-10-16 and 42-38-40 is so chosen as to obtain a calorific balance between the B.T. and H.T. circuits, this distribution being made according to the load losses in the two branches of the circuit, and being capable of adjustment, for example by means of one or two covers 50-50 of a chosen cross-section.

Given that the supercharging air of the engine must be cooled by the second stage 26 of the exchanger 28, down to a temperature lower than that of the lubricating oil which passes into the exchanger 24 (e.g. respectively 50 degrees C. and 70 degrees C.), it can be of advantage, especially in large engines to provide an independent cooling circuit for the lubricating oil in order to make the best use of all the radiators.

Such an arrangement is shown in FIG. 4 where the water/oil exchanger24 is withdrawn from the B.T. circuit 6 which, otherwise, is identical to that in :FIG. 1. The independent circuit 52 comprises the exchanger 24, a pump 54, and a B.T. radiator 56 (or a group of radiators), as well as the connecting pipes 58-6062. The H.T. circuit 4 and the diverted circuit 8 are identical to what was described in relation to FIG. 1, except that two H.T. radiators 10 have been shown (which can be assembled in series or in parallel in the water) so as to constitute two pairs of B.T.-H.T. radiators; one pair 20410 and one pair 56-10.

Such an independent circuit 52 can improve the efiiciency of the radiators and in consequence lower the temperature of the air admitted to the motor, as a result of their better utilisation, without increasing appreciably the construction costs, for it is possible to reduce the output of the pump 22 and the cross-sections of the pipes of circuit 6, as this circuit no longer has to effect the cooling of the lubricating oil.

As an example, there has been shown in FIG. 5, the arrangement in curtain formation of the radiators in the embodiment in FIG. 4. If the cooling system needs for example 28 radiators, one can have 14 radiators 10, 10 B.T. radiators 20 effecting the second stage of cooling of the supercharging air, and four B.T. radiators 56 effecting the cooling of the lubricating oil. Thanks to the invention, each H.T. radiator 10 is in series on the air, with a B.T. radiator (20 or 56), so that all the radiators are put to the best use.

The following will provide an example illustrating the advantages of the inventive cooling system, in the case of a Diesel locomotive engine whose radiators, when the engine is at full power, must evacuate a quantity Q of calories per H.P./ hour, distributed in the followmg way:

Ql==O.43Q for the engine water (H.T. circuit) Q2:0.57Q for the cooling-water for the supercharging air and the lubricating oil (B.T. circuit).

Rough calculation gives the following results, if, for example, the temperatures of the air passing through the radiators are as follows:

B.T. radiator: entry 30 deg. C., exit 50 deg. C. (At 20 deg.).

H.T. radiator: entry 50 deg. 0., exit 95 deg. C. (At 45 deg).

If one supposes that a number N of H.T. radiators are necessary to cool the engine water, the number N of B.T. radiators necessary in a conventional cooling system (i.e. where the B.T. circuit effected cooling of the lubricating oil, and the entire cooling of the supercharging air) will be:

It can therefore be seen that in a conventional system the total number of radiators is N +3N =4N and that /3 of the B.T. radiators will be in series on the air with the B.T. radiators, thus they will work badly and that the final temperature of 50 deg. C. will not be maintained.

With a system with a diverted H.T. system according to the invention, such for example as that shown in FIG. 1

each B.T. radiator can work paired with an H.T. radiator, so that: the B.T. radiators can evacuate:

At 20 m -a the H.T. radiators can evacuate:

As it has been seen that N H.T. radiators can evacuate 0.43Q, it will be necessary, in order to evacuate 0.69Q, a number N" of radiators (H.T.) such as 0.69 II N -N -1.6N

Therefore there will be 1.6N H.T. radiators and 1.6N B.T. radiators, i.e. 3.2N radiators in all instead of 4N with the conventional system. The saving in construction costs of radiators is 20%, and the exit temperature of 50 deg. C. for the B.T. radiators will be maintained.

It can be seen, moreover, that the diverted circuit will have to evacuate 0.69Q0.43Q=0.26Q in order to balance the two B.T. and H.T. circuits.

In the case of the embodiment in FIG. 4, the B.T. circuit added 52, whose function is to maintain the lubricating oil at a temperature suitable (e.g. 70 deg. C.) for the water of this circuit, a temperature higher than that of the water of circuit 6, gives a better efliciency to the radiators 20 which can keep the supercharging air at a temperature lower than the 50 deg. C. aforementioned, whence an improvement in the engines functioning is achieved.

The total water output of the B.T. circuits, i.e. the output circulating in the circuits 6 and 52 will be about half of the output which circulated in the circuit 6 of FIG. 1, which makes assembly easier.

Naturally, the invention is in no way limited to the examples described and illustrated. It is capable of numerous variations within the field of the specialist, in the framework of the uses envisaged, without however going beyond the scope of the invention.

Thus it is that in the case of a supercharged motor comprising only one single cooling circuit, e.g. an engine with a low compression ratio, such as those in question before, the cooling circuit is limited to the following elements indicated in FIG. 2 or 4; a main branch which comprises the pump 12, the pipeline 18 and the engines waterjackets, into which therefore the whole output of the pump passes; a primary diverted branch comprising the pipes 14-16 and the radiators 10 into which there therefore passes only a fraction of the pumps output; a secondary diverted branch, in parallel on the primary diverted branch, comprising the pipes 40-42 as well as the heatexchanger 38 through which passes the supercharging air.

I claim:

1. A cooling system for a supercharged internal combustion engine having a liquid cooling jacket and a supercharger inlet means; a first heat-exchanger means disposed in said supercharger inlet means arranged to absorb heat from the air passing therethrough; a second heat-exchanger means disposed in said inlet means between said first heat-exchanger means and said engine arranged to absorb heat from the air passing therethrough; a first high-temperature cooling liquid circuit including a first air-cooled radiator means, a first circulation pump means and said cooling jacket of said engine; a low-temperature cooling liquid circuit including a second aircooled radiator means, a second circulation pump means and said second heat-exchanger means for cooling supercharger air passing through said second heat-exchanger means down to a relatively low-temperature; and a second high-temperature cooling liquid circuit, including said first heat-exchanger means; said second high-temperature cooling liquid circuit being interconnected to said first high-temperature cooling liquid circuit at a point located near the liquid outlet of the engine and at a point located near the inlet side of said first circulation pump for cooling the air passing through the first heat-exchanger means down to a relatively high temperature before it passes through said second heat-exchanger means.

2. A cooling system for supercharged internal combustion engines as defined in claim 1 wherein said first air-cooled radiator means comprises a first pair of aircooled radiators arranged in series in the air of the surroundings used to cool said first pair of radiators and said second air-cooled radiator means includes a second pair of radiators arranged in series in the air of the surroundings used to cool said second pair of radiators.

3. A cooling system for supercharged internal combustion engines as defined in claim 1 wherein said second heat-exchanger means comprises at least one water/ supercharger air heat-exchanger; said second air-cooled radiator means comprises low-temperature radiators and said low-temperature liquid cooling circuit further includes a water/engine lubricating oil heat-exchanger.

4. A cooling system for supercharged internal combustion engines as defined in claim 2 wherein said second heat-exchanger means com-prises at least one water/ supercharger air heat-exchanger; said second air-cooled radiator means comprises low-temperature radiators; and said system further includes an auxiliary cooling circuit which includes at least one water/lubricating oil heatexchanger, a pump and low-temperature radiators.

References Cited WENDELL F. BURNS, Primary Examiner.

US. Cl. X.R. l23-119; 6013 

